let arr = [
  { id: 1, name: "部门1", pid: 0 },
  { id: 2, name: "部门2", pid: 1 },
  { id: 3, name: "部门3", pid: 1 },
  { id: 4, name: "部门4", pid: 3 },
  { id: 5, name: "部门5", pid: 4 },
];

function arrayToTree(items) {
  const result = []; // 存放结果集
  const itemMap = {}; //

  // 先转成map存储
  for (const item of items) {
    itemMap[item.id] = { ...item, children: [] };
  }

  console.log(itemMap);
  for (const item of items) {
    const id = item.id;
    const pid = item.pid;
    const treeItem = itemMap[id];
    if (pid === 0) {
      result.push(treeItem);
    } else {
      if (!itemMap[pid]) {
        itemMap[pid] = {
          children: [],
        };
      }
      itemMap[pid].children.push(treeItem);
    }
  }

  return result;
}
arrayToTree(arr);
